The present invention relates to a robotic wash cell using a recycled, pure water system that includes a six-axis robotic arm and end effector equipped with nozzles that spray unheated, solvent free, high-pressure water to clean oil films from or debur an object by maintaining the nozzles in close proximity and substantially normal to each surface being cleaned or edge being deburred.
Various factors affect the design of a robotic wash system. These factors include the size, shape and texture of the object or item being cleaned, the material or contaminant being removed, and whether the working fluid is recycled, contains a cleaning solvent or is heated. Robotic wash systems for small and mid size objects, such as cars, car body carriers and painting masks frequently use a wash cell or booth that encloses the item and wash system. Larger objects such as airplanes, ship cargo holds and storage tanks, frequently require a portable robot that is brought to or placed inside the object being cleaned. Some systems are designed to remove paint from the surface of the item while others are designed to remove a contaminant such as oil or grease. Some criteria allow the spray to slightly erode the item while others do not. Examples of various robotic washing and cleaning devices are discussed and shown in U.S. Pat. No. 4,817,653 to Krajicek, U.S. Pat. No. 5,038,809 to Rodgers, U.S. Pat. No. 5,358,568 to Okano, U.S. Pat. No. 5,248,341 to Berry and U.S. Pat. No. 5,454,533 to Grant, the disclosures of which are incorporated by reference herein.
Robotic wash systems include a variety of components. They typically include a robotic device and corresponding control system, a working fluid for washing the object, a pump to pressurize the fluid, nozzles to spray the fluid at the object, and an end effector or frame to support the nozzles. Detergents or other chemical solvents are usually added to the wash spray to improve cleaning effectiveness. The wash system can include a closed room or cell that contains the robotic arm, object being cleaned and working fluid spray. Wash cells help prevent work related injuries and accidents that can arise due to inadvertent contact with the rapidly moving robotic arm or its heated, pressurized spray. Wash cells also help contain the spray and its chemical that enter the air in the form of a mist or increased humidity. This helps maintain the manufacturing plant and its air supply in a desirable condition. Some examples of wash cells are described in U.S. Pat. No. 4,220,170 to Hebert, U.S. Pat. No. 4,629,409 to Satoh and U.S. Pat. No. 4,850,382 to Williams, the disclosures of which are incorporated by reference herein.
Wash systems are often designed to recycle the working fluid after it is sprayed. The sprayed fluid is typically collected and passed through one or more filters or separators to remove the contaminants and debris. Examples of some conventional recycling wash systems are described in U.S. Pat. No. 4,029,114 to Wiltrout, U.S. Pat. No. 4,652,368 to Ennis, U.S. Pat. No. 5,059,332 to Satoh, U.S. Pat. No. 5,501,741 to McMahon, U.S. Pat. No. 5,593,598 to McGinness, U.S. Pat. No. 5,665,245 to Kloss, U.S. Pat. No. 6,402,855 to Damron and RE 37,674 to Carter, the disclosures of which are incorporated herein.
Conventional robotic wash systems have difficulties cleaning contaminants such as oil and grease from an object, particularly when the working fluid is being recycled. Oil and grease can leave a thin film on the surface of the object even after it is washed. This film causes manufacturing problems when the object is being handled in other areas of the plant. Conventional wash systems add solvents and heat to help break down the oil or grease. These solvents and the increased mist and humidity due to the heat can damage the components and joints of the robotic arm. Yet, waterproofing the robotic arm is expensive and difficult to maintain. Heated working fluids also increase the rate at which biological contaminants grow in the fluid system and inside the wash cell. These biological contaminants pose a health hazard to the people working in the plant, and can damage the robotic arm and other components in the wash system.
Solvents also make it difficult to recycle the working fluid. Solvents tend to mix or otherwise combine with the water and oil or grease to create emulsions. These emulsions are difficult to filter out or separate from the water without using expensive and bulky filtration system. The oil emulsions adhere to the pipe walls and clog the nozzles and other components in the system. The emulsion build up on the pipes and components creates a resilient layer that has a dampening effect on the pressurized system. The dampening effect causes delays to pressure changes in the working fluid, such as when the system is turned on or off. The oil emulsions also attacks the pump seals and other components in the system. Economical and efficient high-pressure water pumps have seals that require the working fluid to have 5 parts per million (ppm) of oil or less to avoid frequent maintenance shut downs. The entire wash system may need to be shut down and flushed every few hundred hours to clean, refurbish or replace the piping, components and pump seals. This maintenance is expensive and can render the system unacceptable for many industrial applications where such delays adversely affect the overall efficiency of the entire manufacturing process.
Another problem with conventional wash systems is that they require large quantities of water and take up large amounts of floor space. The filters and separator in the recycling system require a significant amount of time to separate the contaminants and emulsions from the water in order to achieve the desired purity levels of the system. As a result, a large quantity of inactive water must remain in these filters and separators in order to support a relatively small volumetric flow through the spray nozzles. These filters and separators are also relatively large so that even a small wash cell requires a significant amount of plant floor space.
An additional problem with conventional robotic wash systems is that they lack the range of motion needed to use pure water to completely remove contaminants like oil from an object, particularly objects having more complex shapes. Conventional five-axis robotic arms and devices are not suitable for a pure water wash cell system. These robotic arms have difficulty positioning and articulating the spray nozzles to spray directly at or normal to the surface of the object being cleaned. The water sprays strike many surfaces of the object at angles that cannot completely remove an oil film layer. It has been found that angles of greater than about 7xc2x0 degrees from normal start to deteriorate the cleaning effectiveness of a pure water spray for the purpose of removing oil and grease from the surfaces of an object. While a conventional five-axis robotic arm might be able to wash a flat tray placed in direct alignment with the robotic arm, these arms do not provide a sufficient range of motion to enable them to handle most objects. These robotic arms lack the flexibility to get into the nooks and crannies found in the vast array of items that need to be cleaned in many manufacturing settings. Items with surfaces that face in different directions or are offset from the main axis of the robotic arm, or items having a number of projections or recesses in those surfaces are particularly troublesome. Five-axis arms also have difficulty or are incapable of cleaning surfaces with small areas that must be avoided to prevent damage to sensitive components.
A further problem with conventional robotic wash systems is that they have a limited spray width. In order to clean an item with a large surface area, the robotic arm must move back and forth across a surface many times. This increases the time the robot needs to get the item through the wash cell and reduces the overall capacity of the system. While some wash systems attempt to increase the spray width by aligning a number nozzle on a bulky frame to repeatedly clean a specific object with a specific shape, these systems are not designed to handle a wide variety of item shapes and sizes found in a manufacturing setting. In addition, the bulky frame may require hundreds of nozzles to clean a large item such as an airplane.
A still father problem with an array of aligned spray nozzles is that the nozzles have to be a certain distance from the surface of the item to perform properly. Adjacent nozzles with diverging sprays tend to intersect each other so that the overall spray pattern completely covers an area in a single pass. These diverging sprays pose problems for robotic applications that manipulate the spray nozzles through several passes over an object, particularly objects with more complex shapes. The width of the diverging spray varies when the nozzle is closer to or further away from the surface being washed. When the nozzles are too close to a surface, there are gaps between adjacent sprays so that the surface is not completely cleaned. When the nozzles are too far from the surface, adjacent sprays intersect, which tends to reduce the cleaning effectiveness of the sprays. This is particularly true for a high-pressure spray system where intersecting portions of spays have significantly reduced pressure and effective cleaning power.
A still further problem with conventional wash systems is that their usefulness is limited to cleaning the item. The systems cannot be adapted to provide an additional function such as deburring the surfaces or edges of the item. Capital expenditures for another robotic cell and fluid system are needed to provide the deburring operation.
A still further problem with conventional wash systems is that the end effector is not able to remove various types of debris from the item so that the wash nozzles can clean the entire item. In a manufacturing setting, debris and garbage such as dirty rags, towels, cans, paper bags can be left on an item moving along a conveyor system leading to the wash cell. The high-pressure water jets do not produce enough volumetric flow to blow this debris off the item during the wash cycle. As a result, portions of the item may be missed. The item may need to be taken off the conveyor system downstream of the wash cell and returned for additional cleaning.
The present invention is intended to solve these and other problems.
The present invention pertains to a robotic wash cell including a six-axis robotic arm and end effector equipped with nozzles that spray unheated, solvent free, pure water at high-pressure to clean or debur objects by maintaining the nozzles in close proximity and substantially normal to each surface being cleaned or edge being deburred. The robotic cell wash is particularly useful for cleaning contaminants such as oil and grease from items having more complex shapes. The six-axis robotic arm positions the nozzles and their sprays substantially normal to each surface being cleaned or deburred. The nozzles produce a multi-zone spray pattern with a continuous effective cleaning zone. A water recycling and pressurizing system collects the used water, separates out the oil and grease contaminants to a level of about 5 ppm, and pressurizes the pure water to about 3,000 psi for washing operations or about 6,000 psi for deburring operations.
The present robotic wash cell and water system invention cleans contaminants such as oil and grease from an object having a solid surface without using solvents, detergents or other cleaning agents. The high-pressure, pure water spray efficiently and thoroughly cleans oil or grease from the surfaces of the item being washed. No significant trace or film of oil or grease remains on the surfaces of the item after it is washed. This is a significant advantage for many manufacturing processes where the presence of an oil or grease film can result in manufacturing problems that would otherwise require the item to be manually cleaned.
The present robotic wash cell and water system invention uses unheated, solvent free pure water as its working fluid. The pure water spray produced by the system does not create significant amounts of water and oil emulsions, such as those associated with wash systems using detergents or other solvents. The ambient temperature of the water spray further reduces the amount of emulsions and significantly reduces the amount of mist and humidity inside the cell. The water spray does evaporate or float in the air as readily as in heated systems. The wash cell has an air filtration system that is able to easily handle the mist and humidity that do occur. As a result, the robotic arm operates in a more friendly environment that is less contaminated with corrosive chemicals, and costly maintenance and waterproofing of the robotic arm are avoided or minimized. The ambient temperature spray also significantly reduces the growth of biological contaminants in the wash cell and water system that would otherwise pose a health risk to the people in the plant or damage the robotic arm and other components in the system.
The present robotic wash cell invention can thoroughly cleans objects by articulating its six-axis robotic arm to aim its high-pressure, pure water spray substantially normal to each surface being cleaned and maintain the nozzle in close proximity to these surfaces as the robotic arm and water spray move across them. The water is preferably pressurized to about 3,000 psi and maintained within a continuous efficient cleaning zone about eight to ten inches from the surface of the object during each cleaning pass. The sixth axis of the robotic arm allows it to articulate the water spray as it moves along a cleaning path along a particular surface so that the spray remains normal or substantially normal to that surface, as well as at the edge or intersection of two adjacent surfaces. This articulating, high-pressurized water spray maintains its cleaning effectiveness throughout the cleaning of the object. The robotic wash system is able to substantially completely clean oil or grease films from many surface materials, including metal, plastic, ceramic or painted surfaces in a cost effective and time efficient manner. The wash system has been found to be particularly effective at cleaning oil and grease films from the aluminum surfaces of many automotive components.
The present pure water wash system conserves water. Chemical emulsions that commonly occur in heated, solvent or detergent based wash systems are avoided so that the water supply can be economically recycled. The filtration system includes a small tank, and relatively inexpensive filters, plate separator for removing the oil contaminants and ultraviolet germicidal treatment unit to inhibit the growth of germs and bacteria Expensive and bulky filtration, separation and treatment systems are not necessary.
The present robotic wash cell and recycled pure water system achieves a high level of water purity and requires minimal maintenance. The system can remain operating for 6,000 hours between scheduled maintenance intervals. This significantly long operating duration increases the capacity and overall efficiency of the system and the entire plant, particularly plants having assembly lines and just-in-time manufacturing. The present robotic wash system also achieves water pressures of 1,000 to 6,000 psi by using conventional high-pressure pumps with low maintenance ring seals. By eliminating solvents and the emulsions they produce, the system is able to achieve a water purity level having suspended solids of 30 microns or less, oil concentrations of 5 ppm or less, and a water temperature of 120xc2x0 F. or less. This water purity and low temperature allows the system to use a conventional ring seal pump capable of achieving 6,000 psi. This pump also avoids heating the water. Expensive pumps with packed seals and short maintenance intervals are not necessary. In addition, oil emulsions that would otherwise adhere to the pipe walls or otherwise clog the nozzles and other components in the system are minimized to help achieve the long operating duration of the system. As a result, the present invention is ideally suited for many industrial applications.
Another advantage of the present wash system invention is that it requires a relatively small quantity of water and fits into a relatively small area of floor space. The oil separator fits inside a relatively small 100 to 250 gallon tank. A large portion of the water supply remains actively flowing through the pipes, pumps and spray nozzles. The size of the filters and separator are also small enough to justify a relatively small wash cell to accommodate a plant with a limited amount of available floor space.
A further advantage of the present robotic wash cell invention is its ability to wash a wide variety of objects, including those with more complex shapes. The robotic wash cell includes a six-axis robotic arm that accommodates a wide variety of objects. Although the robotic arm is secured to the floor, ceiling or other supporting surface in the wash cell, the robotic arm is flexible enough to allow a range of motion and articulation of the nozzles and water spray to reach the various surfaces of a wide variety of objects. The robotic arm directs the end effector, nozzles and spray normal to each of the various surfaces while maintaining the nozzles in close proximity to each surface being cleaned. The robotic arm is able to follow the contour of the object including its projections and recesses. The robotic arm can also move in closer to clean some areas more vigorously than others, or avoid designated areas that should not be cleaned to avoid damaging a sensor or other sensitive part. Accordingly, the robotic wash cell is suitable for a wide variety of commercial applications and manufacturing settings.
A still further advantage of the present robotic was h system is its relatively wide spray width. While keeping the weight of the end effector to a minimum, the present invention uses a limited number of two or more nozzles aligned to produce a spray pattern with a continuous working region of sufficient width to quickly clean an item with a large surface are. The robotic arm is programmed to move over the contours of the object in a multi-direction, multi-pass manner. By aligning two or more nozzles, the robotic wash cell is able to effectively clean larger or more complexly shaped objects in relatively few wash paths. This increases the through speed or capacity of the robotic wash cell so that it can clean a large number of objects in a relatively short period of time.
A still further advantage of the robotic wash cell is that its individual high-pressure sprays are offset so that they do not intersect. Each nozzle produces a diverging spray so that adjacent sprays begin to overlap at a set distance of about eight inches from the nozzle. Yet, each nozzle is offset or rotated a slight amount about its central axis so that adjacent sprays are parallel but do not intersect. As a result the entire spray pattern strikes the surface being cleaned with a substantially uniform pressure or cleaning power. The amount of pressure or cleaning power depends on the distance the nozzle is from the surface being cleaned, not whether the surface is in an area of intersecting sprays with reduced cleaning power. When the nozzles are positioned about eight to ten inches from the surface being cleaned, adjacent sprays do not leave a gap between them. Instead, they create a continuous, substantially uniform zone with an effective cleaning power that the robotic arm is free to manipulate to efficiently clean items with complex shapes.
A still further advantage of the present wash system is its ability to debur the surface of the item. The wash nozzles on the end effector can readily be replaced with debur nozzles. The high-pressure pump is then easily switched to pressurize the water to about 6,000 psi or more by reducing the volumetric rate of water supplied to the pump and nozzles. Capital expenditures for an additional deburring station are avoided.
A still further advantage of the present wash system is its ability to clear or remove various types of debris from the item so that it can clean or debur the entire item. The end effector includes nozzles for blowing a large volume of air that combines with the high-pressure water spray to blow or sweep away any debris on the item. Debris and garbage such as dirty rags, towels, cans, paper bags that are inadvertently left on an item in a manufacturing setting are swept away by the combined sprays. As a result, the system is capable of reliably cleaning the entire item without missing areas that may be covered by debris and garbage.
Other aspects and advantages of the invention will become apparent upon making reference to the specification, claims and drawings.